JP2017014405A - Polypropylene and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide polypropylene having enhanced crystallization speed and excellent in molding processability while maintaining physical properties such as the melting point and a manufacturing method therefor.SOLUTION: There is provided polypropylene containing a propylene unit (A) and an aromatic comonomer unit (B), where percentage content of the aromatic comonomer unit (B) is 0.005 mol% to 0.05 mol% based on total amount of a monomer unit constituting the polypropylene.SELECTED DRAWING: None

Description

  The present invention relates to polypropylene and a method for producing the same.

  Polypropylene (PP) is lightweight, relatively inexpensive, has a high melting point, and has various advantages such as excellent physical property balance, chemical resistance, molding processability, and recyclability. As widely used.

  The physical properties of PP that can have a significant influence on the molding process of a resin composition containing PP and the use of a molded product include crystallization speed, crystallinity, crystal structure, melting point, glass transition temperature, and the like. Of these, the crystallization speed is the most important factor in determining the cycle time of the molding process. Further, the crystallinity and crystal structure can affect each physical property such as melting point and mechanical properties. The crystallization speed of the resin composition containing PP and PP can be adjusted by various means. The crystallization rate can be adjusted by, for example, molding processing conditions, and can also be adjusted by an additive such as a crystal nucleating agent (nucleating agent) or a complex with another polymer.

  For example, Patent Document 1 discloses a composite of an aromatic phosphate metal salt component represented by a specific structural formula and an aliphatic organic acid metal salt component represented by a specific structural formula on syndiotactic polypropylene. An invention relating to a syndiotactic polypropylene composition in which the crystallization rate and the molding cycle are improved by blending a nucleation product comprising a body is disclosed.

  It is known that primary structures such as molecular weight, molecular weight distribution and stereoregularity in polypropylene can affect crystallization behavior. However, regarding the molecular weight and molecular weight distribution of polypropylene, the range of numerical values that can be taken is limited depending on the molding process of the resin composition containing polypropylene, the purpose of the molded product, and the like. Further, many attempts have been made to improve the stereoregularity of polypropylene with a polymerization catalyst so far, and it has been difficult to further improve the stereoregularity.

  It is also known that the introduction of a functional group to polypropylene can affect the crystallization behavior of polypropylene. However, when functionalization of polypropylene (for example, modification by graft polymerization, etc.) is performed, the crystalline lamella structure cannot grow due to the functional group introduced into the side chain, resulting in a decrease in melting point and a decrease in crystallinity. There is a possibility that stability and mechanical strength are lowered, and there is a possibility that molding processability is lowered due to an increase in viscosity due to interaction between functional groups.

JP 2008-231143 A

  An object of the present invention is to provide a polypropylene having improved crystallization speed and excellent molding processability while maintaining physical characteristics such as a melting point and a method for producing the same.

  The polypropylene according to the present invention is a polypropylene containing a propylene unit (A) and an aromatic comonomer unit (B), and the content of the aromatic comonomer unit (B) is based on the total amount of monomer units constituting the polypropylene. It is 0.005 mol% or more and 0.05 mol% or less.

  The aromatic comonomer unit (B) is preferably a monomer unit derived from at least one compound selected from styrene and 1-allylnaphthalene.

  In addition, the method for producing polypropylene according to the present invention is a method for producing by polymerizing a monomer raw material containing at least propylene and a compound having an ethylenically unsaturated group and an aromatic ring in an inert solvent in the presence of a catalyst. It is.

  According to the above configuration, it is possible to provide a polypropylene having improved crystallization speed and excellent moldability while maintaining physical characteristics such as a melting point.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

<Composition of polypropylene>
The polypropylene (hereinafter also referred to as “PP”) according to the present embodiment is a polymer that contains a propylene unit (A) as a main component and further contains a small amount of an aromatic comonomer unit (B) as a constituent unit. In the present specification, “polypropylene” or “PP” does not mean only a polymer composed only of a homopolymer of propylene, a propylene unit (A) and an aromatic comonomer unit (B). A copolymer containing a constituent unit other than the unit (A) and the aromatic comonomer unit (B) is also included. For example, the content of the propylene unit (A) is 90% with respect to the total amount of monomer units constituting the PP. Also included is a copolymer having a mol% or more, preferably 95 mol% or more, and the remaining monomer units derived from a comonomer other than propylene.

  In the present specification, the description of “unit” or “monomer unit” in “propylene unit (A)” and “aromatic comonomer unit (B)” refers to the polymerized monomer raw material in the polymer structure. Derived structural unit. In the present specification, the “content ratio” of the monomer units constituting PP means the ratio of the abundance of the monomer units to the total amount (total) of monomer units constituting PP, and is expressed in mol%. The

  The aromatic comonomer unit (B) contained in PP of the present embodiment is a monomer unit derived from a compound having an ethylenically unsaturated group and an aromatic ring (hereinafter also referred to as “aromatic comonomer (b)”).

  The aromatic comonomer (b) is not limited as long as it is a compound having an ethylenically unsaturated group and an aromatic ring. For example, an aromatic comonomer (b) having an alkenyl group having an ethylenically unsaturated group as a substituent on the aromatic ring. Group compounds. Examples of the alkenyl group having an ethylenically unsaturated group include a vinyl group, an allyl group (propylene group), and a 1,2-butene group. The aromatic ring has, for example, a substituent such as a methyl group. And an optionally substituted phenyl group and naphthyl group. Specific examples of the aromatic comonomer (b) include styrene, allylbenzene, vinylnaphthalene (1-vinylnaphthalene or 2-vinylnaphthalene) and allylnaphthalene (1-allylnaphthalene or 2-allylnaphthalene). .

  In the PP of this embodiment, the content of the aromatic comonomer unit (B) is 0.005 mol% or more and 0.05 mol% or less with respect to the total amount of monomer units constituting the polypropylene of this embodiment. Furthermore, the content of the aromatic comonomer unit (B) is preferably 0.005 mol% or more and 0.03 mol% or less.

  The PP of the present embodiment includes an aromatic comonomer unit (B) at a content in the above range, and thus has a melting point and the like as compared with PP having the same composition except that the aromatic comonomer unit (B) is not included. The crystallization rate can be improved while substantially maintaining the physical characteristics. Since the PP of the present embodiment having an improved crystallization speed is excellent in molding processability, it becomes possible to shorten the cycle time when the resin composition containing the PP of the present embodiment is molded.

  In the PP of this embodiment, for example, when the aromatic comonomer unit (B) is a monomer unit having one aromatic ring such as a monomer unit derived from styrene, the content of the aromatic comonomer unit (B) is It is preferable that it is 0.015 mol% or more and 0.05 mol% or less, and it is more preferable that it is 0.018 mol% or more and 0.03 mol% or less. When the aromatic comonomer unit (B) is a monomer unit having two aromatic rings such as a monomer unit derived from 1-allylnaphthalene, the content of the aromatic comonomer unit (B) is 0.005 mol%. It is preferable that it is 0.03 mol% or more.

The content of the aromatic comonomer unit (B) in PP is derived from the absorption intensity of the peak derived from the aromatic ring in the ¹ H-NMR spectrum and the alkyl group as the main chain in accordance with the known ¹ H-NMR measurement method. It is calculated | required by comparing with the absorption intensity of the peak to do. Moreover, the content rate of the aromatic comonomer unit (B) in PP can also be calculated | required according to the method by the well-known ¹³ C-NMR measurement similarly to the measuring method of the content rate of the following alpha-olefin comonomer unit (C). .

  The PP of this embodiment may be composed of only a propylene unit (A) and an aromatic comonomer unit (B), and an α-olefin comonomer other than the propylene unit (A) and the aromatic comonomer unit (B). A comonomer unit such as unit (C) may further be included.

  The α-olefin comonomer unit (C) is not particularly limited as long as it is a monomer unit derived from an α-olefin comonomer other than propylene (hereinafter also simply referred to as “comonomer (c)”). Specific examples of the comonomer (c) include linear monoolefins such as ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene, 3-methyl-1-butene, Examples thereof include branched monoolefins such as 3-methyl-1-pentene and 4-methyl-1-pentene. As the comonomer (c), only one type may be used, or two or more types of comonomer (c) may be used.

  In the PP of the present embodiment, the arrangement when the α-olefin comonomer unit (C) is included is not limited. For example, the propylene unit (A) and the α-olefin comonomer unit (C) are randomly arranged. The copolymer may be a random copolymer, or may be a block copolymer in which each of the propylene unit (A) and the α-olefin comonomer unit (C) forms a chain block.

The content ratio of the propylene unit (A) and the α-olefin comonomer unit (C) in PP is determined from the intensity of the peak based on each carbon atom in the ¹³ C-NMR spectrum of PP according to a known method by ¹³ C-NMR measurement. It is done.

Although the stereoregularity (tacticity) of PP of this embodiment is not particularly limited, for example, PP having an isotactic pentad fraction (mmmm fraction) of 90 mol% or more is preferable. The stereoregularity of PP is measured by analysis of PP using ¹³ C-NMR. The mmmm fraction is an index indicating the isotacticity of a polymer such as PP.

<Measurement of physical properties of polypropylene>
The crystallization rate, melting point (crystal melting peak temperature) Tm, and crystallinity Xc of PP are measured by a conventional method using a differential scanning calorimeter (DSC).

  Although the molecular weight of PP of this embodiment is not specifically limited, For example, PP whose weight average molecular weight Mw is 2000 or more, Preferably it is 10,000 or more is mentioned. The upper limit of the weight average molecular weight Mw is practically several million. The weight average molecular weight can be measured as a weight average molecular weight Mw converted to standard polystyrene using GPC (gel permeation chromatography).

<Production method of polypropylene>
In the PP of this embodiment, when polymerizing propylene (in some cases, comonomer other than propylene and propylene), by carrying out a polymerization reaction in the presence of an aromatic comonomer (b) having an ethylenically unsaturated group and an aromatic ring. A known PP production method can be applied as the production method. For example, the PP according to this embodiment can be prepared by a known polymerization method such as slurry polymerization, bulk polymerization, and gas phase polymerization.

  Hereinafter, the case where PP of this embodiment is manufactured by slurry polymerization will be described. Production of PP of this embodiment by slurry polymerization is carried out, for example, in a polymerization reaction tank in the presence of a catalyst, a co-catalyst and a chain transfer agent added as necessary, in an inert solvent. It is carried out by polymerizing a monomer raw material containing at least (b). As a method for producing the PP of this embodiment by slurry polymerization, the polymerization reaction may be performed by either a batch method or a continuous method.

  As the solvent used in the production of PP of this embodiment, any monomer raw material containing a compound having propylene and an ethylenically unsaturated group and an aromatic ring, and any solvent inert to these polymers are used. For example, aliphatic hydrocarbons such as pentane, isopentane, hexane, heptane, and octane; alicyclic hydrocarbons such as methylcyclopentane and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; And halogen derivatives. These can be used alone or in combination of two or more.

  The catalyst used for the production of PP of the present embodiment is not particularly limited as long as it is a solid catalyst containing a transition metal component, which is usually used as an olefin polymerization catalyst. For example, Ziegler-Natta (Ziegler- Natta) catalysts, metallocene catalysts, and other known catalysts can be used. Examples of the Ziegler-Natta catalyst include a catalyst comprising a combination of a titanium compound and a co-catalyst (donor) such as triethylaluminum or methylalumoxane (MAO). Both are supported on a carrier such as magnesium halide. It is also used as a supported catalyst. Examples of the metallocene catalyst include a catalyst obtained by adding a promoter such as an alkylaluminum compound to a complex of a cyclopentadienyl derivative and a transition metal.

Although the usage-amount of the catalyst used is adjusted with the kind of catalyst, it can be 10 ^<-7 > ^-10 < ³ > mmol / L as a transition metal atom with respect to a solvent, for example.

  Examples of the cocatalyst used in the production of the PP of the present embodiment include alkylaluminum, aluminoxane, Lewis acid, fluoroborane, alkylboron, and alkylboron ammonium salt. More specifically, methylaluminoxane (MAO), ethylaluminoxane (EAO), isobutylaluminoxane (IBAO), trimethylaluminum (TMA), triethylaluminum (TEA), triisobutylaluminum (TIBA) and the like can be mentioned. Or a mixture of two or more.

  The amount of the cocatalyst used in the slurry polymerization is adjusted depending on the type of the catalyst and the cocatalyst. For example, the molar ratio of the metal atom (Al atom or the like) in the cocatalyst to the transition metal atom in the catalyst It can be in the range of 1 to 100,000. The catalyst and the cocatalyst may be charged separately in the polymerization reaction system, or may be charged in advance after both have been brought into contact with each other. Preliminary polymerization in which both are brought into contact with each other in the presence of a monomer raw material to be polymerized to partially polymerize a small amount of monomer may be performed in advance.

  As a monomer raw material used for manufacture of PP of this embodiment, propylene and an aromatic copolymer (b) are included, and also a comonomer (c) may be included. Each of these monomer raw materials is supplied according to the physical properties of each monomer raw material.

  In the production of PP of this embodiment by slurry polymerization, propylene can be supplied into the polymerization reaction system by, for example, supplying gas in the gas phase part of the polymerization reaction tank and dissolving it in a solvent. What is necessary is just to supply sequentially according to consumption of the propylene by a polymerization reaction, when manufacturing PP of this embodiment by a continuous type.

  The aromatic comonomer (b) is added to the solvent in the polymerization reaction tank in advance or during the sequential polymerization reaction prior to the polymerization reaction. In the production of PP of the present embodiment, depending on the solvent used and the polymerization reaction conditions, the aromatic comonomer (b) is obtained in such an amount that PP containing the aromatic comonomer unit (B) in the above specific range is obtained. ) To the polymerization reaction system.

  In the production of PP of this embodiment by slurry polymerization, the amount of the aromatic comonomer (b) added to the solvent is, for example, 1 to 30 mmol / L, depending on the type of the inert solvent and the polymerization reaction conditions. Can do. In the production of PP of this embodiment by slurry polymerization, when a compound having one aromatic ring such as styrene is used as the aromatic comonomer (b), the addition amount of the aromatic comonomer (b) to the solvent is 7.5 to 20 mmol / L is preferable. When a compound having two aromatic rings such as 1-allylnaphthalene is used as the aromatic comonomer (b), the amount of the aromatic comonomer (b) added to the solvent is 5 to 15 mmol / L. It is preferable that What is necessary is just to add sequentially according to consumption of the aromatic comonomer (b) by a polymerization reaction, when manufacturing PP of this embodiment by a continuous type.

  Depending on the state of the substance, comonomer (c) is sent to the gas phase part of the polymerization reaction tank in the same manner as propylene if it is a gas, and is charged into a solvent if it is liquid or solid. The content rate of the α-olefin comonomer unit (C) in PP can be adjusted by, for example, the supply amount of the comonomer (c) to the polymerization reaction system.

  The PP of this embodiment can be produced by the above polymerization method. In addition, the PP of the present embodiment is not limited to the above-described slurry polymerization, but bulk polymerization using propylene as a solvent without substantially using an inert solvent, or substantially in the gas phase without a liquid phase. It can be produced by a known production method such as gas phase polymerization for carrying out polymerization.

  The above-described production method for producing PP containing the aromatic comonomer unit (B) at a content of 0.005 mol% to 0.05 mol% in the present embodiment provides a method for improving the crystallization rate of PP. To do. This method for improving the crystallization rate of PP is compared with PP produced by the same method except that it does not contain the aromatic comonomer unit (B). The present invention provides a method for improving the crystallization rate of PP while substantially maintaining stereoregularity and crystallinity.

  The PP of the present embodiment is provided as a resin composition containing the PP of the present embodiment depending on the purpose of use. The resin composition may contain only the PP of the present embodiment as a resin component, or other resins other than the PP of the present embodiment, such as polyethylene, PP other than the PP of the present embodiment, A resin composition mixed with other poly α-olefins such as polybutene and poly-4-methylpentene-1, polyester, polyamide, polycarbonate, ABS resin, elastomer, polyvinyl chloride and the like may be prepared.

  The resin composition containing PP according to the present embodiment includes a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a nucleating agent, a lubricant, a flame retardant, an antiblocking agent, a colorant, and an inorganic material as necessary. Alternatively, various additives such as organic fillers may be contained.

  The use of PP of this embodiment and the resin composition containing this is the same as that of conventional PP, and is not limited. Examples of applications such as PP of this embodiment include resin parts for automobiles such as bumpers, dashboards, and instrument panels; resin parts for household appliances such as refrigerators, washing machines, and vacuum cleaners; Household goods; Storage containers such as tanks and bottles; Medical molded products such as syringes, catheters and medical tubes; Building materials such as wall materials, flooring materials and wallpaper; Wire covering materials; Agricultural materials; Foods such as wraps and trays Packaging materials; molded products for food use such as container bottles, cups, storage containers; and cushioning materials such as foam insulation and foam cushioning materials.

  Hereinafter, based on an Example, embodiment of this invention is described more concretely. In addition, this invention is not limited to a following example.

<Physical property evaluation>
(Content of aromatic comonomer unit (B))
The prepared PP was dissolved in hexachloro-1,3-butadiene, and ¹ H-NMR measurement was performed at 120 ° C. using a nuclear magnetic resonance (NMR) apparatus (manufactured by BRUKER, AVANCE III type). 1,1,2,2, - with reference to the tetra Chloe Tan -d ^2, chemical shifts derived from an alkyl group peak (7.0～8.5Ppm) chemical shift derived from the aromatic ring peak (0. The content of the aromatic comonomer unit (B) in PP was measured.

(Crystallization speed)
The crystallization rate of PP was determined using a differential scanning calorimeter (DSC) (product name DSC822, manufactured by Mettler). 5 mg of the prepared PP was put into a DSC cell and maintained at 230 ° C. for 10 minutes, and then decreased to 132 ° C. at a rate of 5 ° C./minute to maintain the temperature. In this specification, from the measured DSC curve, the time from the rise of the exothermic peak due to crystallization after holding the temperature to ½ of the peak area (half crystallization time t _1/2 ) is calculated, The reciprocal of the half crystallization time t1 _{/ 2} was taken as the crystallization rate.

(Mmmm fraction)
The prepared PP was dissolved in 2,4-trichlorobenzene, and ¹³ C-NMR measurement was performed at 120 ° C. using a nuclear magnetic resonance (NMR) apparatus (manufactured by BRUKER, AVANCE III type). The number of integrations was 5000 times or more.

(Melting point Tm, crystallinity Xc)
The melting point Tm and crystallinity Xc of PP were determined using a differential scanning calorimeter (DSC) (product name DSC822, manufactured by Mettler). 5 mg of the prepared PP was charged into a DSC cell, and the temperature was increased from 50 ° C. to 200 ° C. at a temperature rising rate of 20 ° C./min, and calorimetric analysis was performed.

[Example 1]
In a sufficiently dried polymerization reaction vessel, 140 parts by mass of n-heptane, 2 mmole of triethylaluminum, and 2 mmole of styrene that had been sufficiently dehydrated and degassed in a nitrogen atmosphere were added. The temperature in the polymerization reaction vessel was set to 50 ° C., and the solvent was saturated by introducing propylene into the polymerization reaction vessel so that the polymerization pressure was 5 atm. To this solvent, 0.01 parts by mass of a magnesium chloride-supported Ziegler-Natta catalyst having a diether internal donor and 8 mmol parts of hydrogen as a chain transfer agent were added, the polymerization temperature was 50 ° C., and the polymerization pressure of propylene Was maintained at 5 atm, and slurry polymerization was performed for 30 minutes.

  After 30 minutes from the start of polymerization, 40 parts by mass of methanol was added to the resulting slurry, and the mixture was stirred for 5 minutes and then filtered. The obtained powdery product was washed with a mixed solution of hydrochloric acid and ethanol (volume ratio 1/4 of hydrochloric acid / ethanol), further washed twice with ion-exchanged water, filtered, Dried. The obtained filtrate was added to 260 parts by mass of xylene heated to 139 ° C. and dissolved, and then this solution was added to 2100 parts by mass of acetone for reprecipitation. The obtained reprecipitate was filtered and dried to prepare 21 parts by mass of PP.

The PP obtained in Example 1 was analyzed by ¹ H-NMR. As a result, the content of styrene comonomer units was 0.020 mol%, and as a result of analysis by ¹³ C-NMR, the mmmm fraction was 93 mol%. Met. The PP obtained in Example 1 was analyzed by a differential scanning calorimeter (DSC). As a result, the melting point Tm was 167 ° C. and the crystallinity Xc was 47% as shown in Table 1 below. The speed was 0.22.

[Example 2]
Polymerization was carried out in the same manner as in Example 1 except that 2 mmol part of 1-allylnaphthalene was added to the solvent instead of styrene. As a result, 18 parts by mass of PP was prepared. The PP obtained in Example 2 was analyzed by ¹ H-NMR. As a result, the content of 1-allylnaphthalene comonomer unit was 0.010 mol%, and analyzed by ¹³ C-NMR, the mmmm fraction was It was 94 mol%. Moreover, as a result of analyzing by DSC about PP obtained in Example 2, as shown in following Table 1, melting | fusing point Tm is 167 degreeC, Crystallinity degree Xc is 48%, Crystallization speed | rate is 0.25. there were.

[Example 3]
Polymerization was carried out in the same manner as in Example 1 except that the amount of styrene added was 3 mmol parts. As a result, 20 parts by mass of PP was prepared. The PP obtained in Example 3 was analyzed by ¹ H-NMR. As a result, the content of styrene comonomer units was 0.022 mol%, and as a result of analysis by ¹³ C-NMR, the mmmm fraction was 93 mol%. Met. Moreover, as a result of analyzing by DSC about PP obtained in Example 3, as shown in following Table 1, melting | fusing point Tm is 167 degreeC, Crystallinity degree Xc is 47%, Crystallization speed | rate is 0.19. there were.

[Example 4]
Polymerization was carried out in the same manner as in Example 1 except that 1 mmol part of 1-allylnaphthalene was added to the solvent instead of styrene. As a result, 20 parts by mass of PP was prepared. The PP obtained in Example 4 was analyzed by ¹ H-NMR. As a result, the content of 1-allylnaphthalene comonomer unit was 0.005 mol%, and analyzed by ¹³ C-NMR, the mmmm fraction was It was 94 mol%. Moreover, as a result of analyzing by DSC about PP obtained in Example 4, melting | fusing point Tm is 167 degreeC as described in following Table 1, Crystallinity degree Xc is 48%, Crystallization speed | rate is 0.19. there were.

[Comparative Example 1]
Polymerization was carried out in the same manner as in Example 1 except that styrene was not added. As a result, 18 parts by mass of PP (propylene homopolymer) was obtained. The PP obtained in Comparative Example 1 was analyzed by ¹³ C-NMR. As a result, the mmmm fraction was 93 mol%. Moreover, as a result of analyzing by DSC about PP obtained by the comparative example 1, melting | fusing point Tm is 168 degreeC as described in following Table 1, Crystallinity degree Xc is 49%, Crystallization speed | rate is 0.18. there were.

[Comparative Example 2]
Polymerization was carried out in the same manner as in Example 1 except that the amount of styrene added was 10 mmol. As a result, 20 parts by mass of PP was obtained. The PP obtained in Comparative Example 2 was analyzed by ¹ H-NMR and ¹³ C-NMR. As a result, the content of styrene comonomer units was 0.064 mol%, and the mmmm fraction was 93 mol%. Moreover, as a result of analyzing by DSC about PP obtained by the comparative example 2, melting | fusing point Tm is 166 degreeC as described in following Table 1, Crystallinity degree Xc is 47%, Crystallization speed | rate is 0.17. there were.

The physical properties and crystallization behavior of PP prepared in Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 1 below.

  As the results of Examples 1 to 4 and Comparative Examples 1 and 2 show, a monomer containing a propylene unit (A) and an aromatic comonomer unit (B), and the content of the aromatic comonomer unit (B) constitutes polypropylene. The polypropylene of 0.005 mol% or more and 0.05 mol% or less with respect to the total amount of the units is the polypropylene of Comparative Example 1 having the same composition except that it does not contain the aromatic comonomer unit (B), and the aromatic Compared with the polypropylene of the comparative example 2 in which the content rate of a comonomer unit (B) exceeds the upper limit of the said range, the crystallization speed improved. Since the crystallization speed was improved, the polypropylenes of Examples 1 to 4 are considered to be excellent in moldability. Moreover, the polypropylene of Examples 1-4 maintained melting | fusing point, stereoregularity, and crystallinity compared with the polypropylene of the comparative example 1 which does not contain an aromatic comonomer unit (B).

Claims (3)

  A polypropylene containing a propylene unit (A) and an aromatic comonomer unit (B), wherein the content of the aromatic comonomer unit (B) is 0.005 mol% with respect to the total amount of monomer units constituting the polypropylene. More than 0.05 mol%, The polypropylene characterized by the above-mentioned.   The polypropylene according to claim 1, wherein the aromatic comonomer unit (B) is a monomer unit derived from at least one compound selected from styrene and 1-allylnaphthalene.   The method for producing polypropylene according to claim 1 or 2, wherein a monomer raw material containing at least propylene and a compound having an ethylenically unsaturated group and an aromatic ring is polymerized in an inert solvent in the presence of a catalyst. The manufacturing method characterized by manufacturing by this.